1. Field of the Invention
The present invention relates to a rotor for a gas turbine having a steam cooled moving blade and an air cooled moving blade.
2. Description of the Related Art
In order to improve the thermal efficiency of a gas turbine, cooling a moving blade for a gas turbine by steam is considered. With such a structural arrangement, it is necessary to provide a new rotor having a passage for supplying steam to the moving blade for the turbine and recovering the steam after performing the cooling function.
In this case, extraction steam from a steam turbine in a combined cycle plant and the like are used as cooling steam. However, for reasons of the cycle of the steam, leakage thereof is limited to the utmost.
FIG. 2 is a cross sectional view of a turbine portion in a gas turbine having a conventional steam cooled moving blade. As shown in FIG. 2, the cooling steam is supplied from the direction of the final stage side of a rotor 31 through a hole 33 having a gap for a spindle bolt 32 of the rotor, and then flows into a front chamber 34 of a first stage moving blade. Then, after cooling a rotor 35 and a moving blade 36 while flowing therethrough, the cooling steam is passed sequentially through a second stage rotor 37 and a second stage moving blade 38 having the same configuration, respectively, so as to cool them, and is then recovered from a cooling steam hole 39 in the final stage rotor 31.
The cooling steam for the steam cooled moving blade is supplied and recovered through the route mentioned above. However, taking efficiency and power output into consideration, it is possible to cool with a slight amount of air in a rear stage (the third stage moving blade shown in the illustrated embodiment).
However, in the structure shown in FIG. 2, since the passage for supplying and recovering the cooling steam is complex, even when only a part of the moving blades is cooled by air, there is no way to provide a passage for cooling air in the rotor end. It is thus difficult to provide for cooling air.